The invention relates to an engine control system, and more particularly to a control system and method for reducing white smoke from the exhaust of a compression ignition engine.
In compression ignition engines, if ignition fails to occur, fuel is expelled from the engine""s exhaust system, as what is commonly referred to as white smoke. As a result of stricter governmental and consumer requirements for fuel economy, performance and emissions, the reduction of white smoke is desirable.
One system for reducing white smoke is described in U.S. Pat. No. 6,009,857, issued to Halser on Jan. 4, 2000. The Hasler patent discloses a cylinder cut-out system for a compression ignition engine having electronic unit injectors. The system includes an electronic controller which receives engine parameter sensor signals. In response to certain conditions of the sensor signals, the electronic controller deactivates a predetermined portion (half) of the electronic unit injectors.
U.S. Pat. No. 5,076,236, issued Dec. 31, 1991 to Yu, discloses a pressure responsive spring-biased cutoff valve for an open nozzle unit fuel injector in an internal combustion engine which allows for the selective operation of a given number of cylinders during an engine low load or idling speed condition for improved white smoke control. The 236 patent recognizes that white smoke can occur under low load or idling speed of an engine, and that xe2x80x9cWhite smoke is a condition that results on engine start-up or low-load motoring conditions due to improper combustion of fuel because of insufficient compression or temperature levelsxe2x80x9d.
In these prior art systems, a predetermined plurality or a given number of cylinders are shut off. The problem with such systems is that they may xe2x80x9cshut offxe2x80x9d a group of cylinders regardless of whether some of the cylinders in that group are firing efficiently or not. This requires additional amounts of fuel to be supplied to the cylinders which have not been disabled, subjecting them to additional work for a predetermined period of time to overcome the disabled cylinders.
Accordingly, it would be desirable to provide a system for reducing white smoke which shuts off only cylinders which are not firing properly.
Accordingly, an object of this invention is to provide an engine control system which efficiently reduces white smoke.
A further object of the invention is to provide such an engine control system which shuts off only cylinders which are not firing properly.
These and other objects are achieved by the present invention, wherein a fuel delivery control system controls fuel delivery for an engine having a plurality of cylinders and a fuel delivery control unit which delivers fuel to each cylinder in response to control signals generated by an electronic control unit. The electronic control unit, for each cylinder, determines a cylinder firing value which is related to a quality of combustion in that cylinder, compares the cylinder firing value to a threshold value, and terminates fuel delivery to only the cylinders for which the comparison indicates unsatisfactory combustion, up to a maximum portion of the total number of cylinders. The cylinder firing value is preferably an engine acceleration value derived from a crank position value generated by an engine crank position sensor. Once a cylinder is cut out, it is shut off for a certain number of times. After this cylinder has been shut off for this certain number of times, it is then provided with a normal amount of fuel so that it can be fired normally.